Be aware of brown widow spiders

Most people seem to be aware of the black widow spider but many people have never heard of the brown widow spider. However, there are four widow spiders found in Florida. They include the southern black widow, northern black widow, red widow and brown widow.

Recently, Okaloosa County Commissioner Carolyn Ketchell mentioned to me that she had more than once seen brown widow spiders in parts of Okaloosa County. Concerned about this and to provide better awareness of this spider, she asked me if I could include an article about this spider in this column.

Most people seem to be aware of the black widow spider but many people have never heard of the brown widow spider. However, there are four widow spiders found in Florida. They include the southern black widow, northern black widow, red widow and brown widow.

All are highly venomous but they are also timid. Bites usually occur when the spider can’t easily get away and becomes unintentionally caught between a person’s skin and clothes or when a person is reaching for something where a widow spider is hiding.

A UF/IFAS Extension publication on brown widow spiders states, “According to Dr. G.B. Edwards, an arachnologist with the Florida State Collection of Arthropods in Gainesville, the brown widow venom is twice as potent as black widow venom. However, they do not inject as much venom as a black widow, are very timid, and do not defend their web.”

Widow spiders are about 1½ inches long with legs extended. All have rounded relatively large abdomens. Both of the black widows are shiny black in color.

The southern black widow possesses the classic red hourglass marking on the underside of its abdomen. The northern black widow has two reddish triangles that resemble an hourglass on the underside of its abdomen and red spots in a row along the middle of its back.

The red widow’s head, thorax and legs are reddish-orange. Its abdomen is black and lacks a complete hourglass but there may be one or two red spots on the abdomen. The brown widow may be gray, light brown or black in color with an orange or yellowish-red hourglass marking on the underside of its abdomen.

The brown widow egg sac looks different as compared to the other widow spiders. They are less than ½ inch in diameter with pointed white silk spikes on the surface which are not present on egg sacs of the other widow spiders. The egg sacs of the other widow spiders have a smooth surface.

The brown widow likes to build its web in secluded, protected areas such as in empty plant containers, mailboxes, building entry way corners, under eaves and inside of old tires.

More information on widow spiders is available from the UF/IFAS Extension Office in your County or from the below links.

http://edis.ifas.ufl.edu/mg206
http://entnemdept.ufl.edu/creatures/URBAN/SPIDERS/brown_widow_spider.htm

You’d be wise to learn to identify these spiders.

Larry Williams is the Extension horticulture agent with the Okaloosa County Cooperative Extension Service, University of Florida. Contact Larry at 689-5850 or email lwilliams@myokaloosa.com.